Selectively hydrogenated styrene-diene block copolymers have been formulated in the past to produce a number of types of adhesive compositions. The basic patent in this field, Harlan, U.S. Pat. No. 3,239,478, shows combinations of these block copolymers with tackifying resins and paraffinic extending oils to produce a wide spectrum of adhesives. However, one of the serious limitations of these adhesive compositions is their relatively low service temperatures. Generally, the highest temperature at which these hydrogenated styrene-diene block copolymers retain useful properties and act like a vulcanized rubber is limited to the softening temperature (T.sub.g) of the styrene end block. Depending upon the molecular weight of the end blocks and the load, these block copolymers can begin to significantly creep or flow at 130.degree.-220.degree. F. For a number of applications it would be very advantageous to have higher service temperatures. For example, these adhesives would be useful in paint shops if the masking tapes produced had a 225-250.degree. F. service temperature.
One means to improve the service temperature of these styrene-diene block copolymers is to mechanically mix a resin with the block copolymer which will increase the softening temperature of the styrene end blocks. However, the resins now currently available for this purpose are limited to service temperature increases of only about 30.degree. F. or less at 30 phr (parts per hundred rubber) loading.
One possible resin not previously disclosed for use in adhesive compositions is a polyphenylene ether resin. These polyphenylene ethers are well known and are described in numerous publications including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,257,358. These polymers are high performance engineering thermoplastics having high molecular weights and possessing relatively high melt viscosities and softening points -- i.e., T.sub.g equals 210.degree. C., &gt;10.sup.4 poise at 315.degree. C. However, the relatively high melt viscosities and softening points are somewhat of a disadvantage in blending with the subject hydrogenated styrene-diene block copolymers.